16, Number 3, March 2009
Aaron A. Sorensen
Alzheimer’s Disease Research: Scientific Productivity and Impact of the Top 100 Investigators in the Field
Abstract: The online availability of scientific-literature databases and natural-language-processing (NLP) algorithms has enabled large-scale bibliometric studies within the field of scientometrics. Using NLP techniques and Thomson ISI reports, an initial analysis of the role of Alzheimer’s disease (AD) within the neurosciences as well as a summary of the various research foci within the AD scientific community are presented. Citation analyses and productivity filters are applied to post-1984, AD-specific subsets of the PubMed and Thomson ISI Web-of-Science literature bases to algorithmically identify a pool of the top AD researchers. From the initial pool of AD investigators, top-100 rankings are compiled to assess productivity and impact. One of the impact and productivity metrics employed is an AD-specific H-index. Within the AD-specific H-index ranking, there are many cases of multiple AD investigators with similar or identical H-indices. In order to facilitate differentiation among investigators with equal or near-equal H indices, two derivatives of the H-index are proposed: the Second-Tier H-index and the Scientific Following H-index. Winners of two prestigious AD-research awards are highlighted, membership to the Institute of Medicine of the US National Academy of Sciences is acknowledged, and an analysis of highly-productive, high-impact, AD-research duos is presented.
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Francesco Panza, Vincenza Frisardi, Cristiano Capurso, Alessia D’Introno, Anna M. Colacicco, Gianluigi Vendemiale, Antonio Capurso, Vincenzo Solfrizzi
Possible Role of S-Adenosylmethionine, S-Adenosylhomocysteine, and Polyunsaturated Fatty Acids in Predementia Syndromes and Alzheimer’s Disease
Abstract: Very recent findings confirmed that S-adenosylmethionine (SAM) can exert a direct effect on glutathione S-transferase (GST) activity. Alzheimer’s disease (AD) is accompanied by reduced GST activity, diminished SAM, and increased S-adenosyl homocysteine (SAH), the downstream metabolic product resulting from SAM-mediated transmethylation reactions, when deprived of folate. Therefore, these findings underscored the critical role of SAM in maintenance of neuronal health, suggesting a possible role of SAM as a neuroprotective dietary supplement in AD. Given recent findings from clinical trials in which ω-3 polyunsturated fatty acids (PUFA) supplementation was effective only in very mild AD subgroups or mild cognitive impairment (MCI), we suggest intervention trials using measures of dietary supplementation (dietary ω-3 PUFA and SAM plus B vitamin supplementation) to determine if such supplements will reduce the risk for cognitive decline in very mild AD and MCI. Therefore, key supplements are not necessarily working in isolation, and the most profound impact, or in some cases the only impact, is noted very early in the course of AD, suggesting that nutriceutical supplements may bolster pharmacological approaches well past the window where supplements can work on their own.
Mark A. Lovell
A Potential Role for Alterations of Zinc and Zinc Transport Proteins in the Progression of Alzheimer’s Disease
Abstract: Although multiple studies have suggested a role for alterations of zinc (Zn) and zinc transport (ZnT) proteins in the pathogenesis of Alzheimer’s disease, the exact role of this essential trace element in the progression of the disease remains unclear. The following review discusses the normal role of Zn and ZnT proteins in brain and the potential effects of their alteration in the pathogenesis of Alzheimer’s disease, particularly in the processing of the amyloid-β protein precursor and amyloid-β peptide generation and aggregation.
Alla B. Salmina (Communicated by Alexander Bolydrev)
Neuron-Glia Interactions as Therapeutic Targets in Neurodegeneration
Abstract: Accumulating evidence suggests that alterations of neuron-glia interactions are associated with the development of neurodegenerative diseases referred to as taupathies. Astrocytes contribute to a variety of functions of neurons, including synapse formation and plasticity, energetic and redox metabolism, and synaptic homeostasis of neurotransmitters and ions. Microglia represent the immune system of the brain and therefore are critically involved in various injuries and diseases. Oligodendrocytes have a role in the regulation of steroid synthesis which is important for neuroprotection against degeneration. Glia-mediated inflammatory response is involved in dramatic changes in the activity of neuritic plaque-associated astrocytes and microglia, and the link between glial activation and neuronal damage or repair has been postulated. In addition, functional relationship between neurons, glial cells, and vascular cells within so-called neurovascular unit is dramatically compromised in Alzheimer’s disease. Therefore, an important role for alterations in synergistic interactions between the cells in pathogenesis of this neurodegenerative disorder has been suggested. Further understanding of the molecular mechanisms of neuron-glia interactions in Alzheimer’s disease may yield novel diagnostic and therapeutic strategies.
Zaldy S. Tan and Ramachandran S. Vasan (Communicated by Sudha Seshadri)
Thyroid Function and Alzheimer’s Disease
Abstract: Thyroid dysfunction has been implicated as a cause of reversible cognitive impairment and as such, the thyroid stimulating hormone has long been part of the screening laboratory test for dementia. Recently, several population-based studies demonstrated an association between hypo- or hyperthyroidism and Alzheimer’s disease. This review discusses the role of thyroid hormone in the normal development and regulation of central nervous system functions and summarizes the studies that have linked thyroid function and dementia risk. Finally, it explores possible biological mechanisms to explain this association, including the direct effects of thyroid hormone on cerebral amyloid processing, neurodegeneration and thyrotropin-mediated mechanisms and vascular mediated enhancement of Alzheimer’s disease risk.
Gabriella Marcon, Giuseppe Di Fede, Giorgio Giaccone, Giacomina Rossi, Anna Rita Giovagnoli, Elio Maccagnano, Fabrizio Tagliavini
A Novel Italian Presenilin 2 Gene Mutation with Prevalent Behavioral Phenotype
Abstract: Presenilin mutations are the main cause of familial Alzheimer’s disease. So far, more than 160 mutations in the Presenilin 1 gene (PSEN1) and approximately 10 mutations in the homologous Presenilin 2 gene (PSEN2) have been identified. Some PSEN1 mutations are associated with a phenotype fulfilling the clinical criteria of frontotemporal dementia. In PSEN2, T122P and M239V mutations presented with severe behavioral disturbances. We describe an Italian patient with a novel PSEN 2 mutation (Y231C) who showed behavioral abnormalities and language impairment as presenting symptoms, with later involvement of other cognitive abilities, particularly of posterior functions.
Benedetta Nacmias, Andrea Tedde, Silvia Bagnoli, Elena Cellini, Bianca Maria Guarnieri, Silvia Piacentini, Sandro Sorbi (Communicated by Silvia Pellegrini)
Implication of GAB2 Gene Polymorphism in Italian Patients with Alzheimer’s Disease
Abstract: A common polymorphism (rs2373115) in the GRB-associated binding protein 2 (GAB2) gene has been recently associated with the risk of developing Alzheimer’s disease (AD) in 644 apolipoprotein E (ApoE) ε4 carriers. In order to assess the involvement of the GAB2 polymorphism in the risk of developing AD, we analyzed the genotype and allele distributions of the GAB2 rs2373115 polymorphism in 579 Italian subjects. Our results support a possible implication of GAB2 genetic variant in AD. However, the observed association was confined to ApoE ε4 non-carriers, thus suggesting a possible role of GAB2 as an independent risk factor for AD.
Michael Hoffmann, Juan Muniz, Elizabeth Carroll, Jorge De Villasante
Cryptococcal Meningitis Misdiagnosed as Alzheimer’s Disease: Complete Neurological and Cognitive Recovery with Treatment
Abstract: A sixty-two year old man, with a background of Alzheimer’s disease for the past three years, acutely presented with imbalance, headaches, and dizziness. Examination revealed a profound frontal disinhibited and dysexecutive syndrome and brain imaging notable for leptomeningeal enhancement; laboratory data confirmed cryptococcal meningitis. Four months after treatment, the patient was normal neurologically, cognitively and neuroradiologically. The specific cognitive impairment and neuroradiological findings may be clues to differing dementia etiologies.
Behnam Sabayan, Mohammad Reza Namazi, Arash Mowla, Seyyed Alireza Moniri
Are Patients with Darier and Haily-Haily Diseases Susceptible to Alzheimer’s Disease? A Theory Based on Abnormal Intraneuronal Ca2+ Homeostasis
Abstract: Calcium is one of the most important intracellular messengers in human brain. Studies show that there is a relationship between altered Ca2+-homeostasis, especially elevation of intracellular calcium, and formation of the hallmark pathological lesions of Alzheimer’s disease. Additionally, Ca2+ is crucial for normal function of the skin, and an abnormal rise in intracellular Ca2+ can consequently lead to the development of two skin disorders: Darier and Hailey-Hailey diseases. As these mutated genes are also highly expressed in the brain and these patients are reported to experience some neuropsychiatric problems, we have hypothesized that patients with these dermatologic diseases may be more prone to the development of Alzheimer’s disease. Further investigation may give us clues to find novel therapeutic targets and agents for modulation of intracellular calcium in neurons.
Yves Rolland, Gabor Abellan van Kan, Fati Nourhashemi, Sandrine Andrieu, Christelle Cantet, Sophie Guyonnet-Gillette, Bruno Vellas (Communicated by Martha Claire Morris)
An Abnormal “One-leg Balance” Test Predicts Cognitive Decline During Alzheimer’s Disease
Abstract: Among elderly without cognitive impairment, poor physical performances have been reported to predict cognitive decline and dementia. Our aim was to explore the predictive value of balance impairment for cognitive decline in 686 community-dwelling Alzheimer’s disease (AD) patients (REAL.FR study). Being unable to stand on one leg for five seconds or more defined balance impairment. Cognitive decline was assessed using the Mini-Mental Status Examination (MMSE) score. Co-morbidities, behavioral and psychological symptoms of dementia (BPSD) using the Neuropsychiatric Inventory score, medication, and level of education were assessed at the hospital. MMSE and balance were reported every six months during two years. Linear mixed model analyses were performed. At baseline, participants with balance impairment (15.2% of the sample) were significantly older, had a lower MMSE score and more BPSD, co-morbidities, and medication. After adjustment for the potential covariates, the presence of balance impairment at each assessment was associated with a mean MMSE decline of 9.2 (1.4) points at two years; having no balance impairment at each assessment was associated with a mean MMSE decline of 3.8 (0.3) points at two years (p<0.001). An abnormal one-leg balance test is a marker of more advanced dementia and predicts a higher rate of cognitive decline.
Lydia Kifle, Daniela Ortiz, Thomas B. Shea
Deprivation of Folate and B12 Increases Neurodegeneration Beyond that Accompanying Deprivation of Either Vitamin Alone
Abstract: Increased homocysteine has in some cases been linked with an increased incidence of Alzheimer’s disease and motor neuron disease. Folate or B12 deficiency increases homocysteine, but controversy exists as to whether their levels also correlate with either disorder. Since their presence within various dietary constituents may confound interpretation, we tested the impact of deprivation of either or both in the closed environment of neuronal cell cultures. Deprivation of either increased cytosolic calcium, reactive oxygen species, intracellular homocysteine, and apoptosis, but deprivation of both fostered substantially larger increases, supporting the notion that both are required for optimal neuroprotection.
Joao P. Lopes, Mathew Blurton-Jones, Tritia R. Yamasaki, Paula Agostinho, Frank M. LaFerla
Activation of Cell Cycle Proteins in Transgenic Mice in Response to Neuronal Loss but not Amyloid-β and Tau Pathology
Abstract: Cell cycle proteins are elevated in the brain of patients and in transgenic models of Alzheimer’s disease (AD), suggesting that aberrant cell cycle re-entry plays a key role in this disorder. However, the precise relationship between cell cycle reactivation and the hallmarks of AD, amyloid-β (Aβ) plaques and tau-laden neurofibrillary tangles, remains unclear. We sought to determine whether cell cycle reactivation initiates in direct response to Aβ and tau accumulation or whether it occurs as a downstream consequence of neuronal death pathways. Therefore, we used a triple transgenic mouse model of AD (3xTg-AD) that develops plaques and tangles, but does not exhibit extensive neuronal loss, whereas to model hippocampal neuronal death a tetracycline-regulatable transgenic model of neuronal ablation (CaM/Tet-DTA mice) was used. Cell-cycle protein activation was determined in these two models of neurodegeneration, using biochemical and histological approaches. Our findings indicate that Cdk4, PCNA and phospho-Rb are significantly elevated in CaM/Tet-DTA mice following neuronal death. In contrast, no significant activation of cell-cycle proteins occurs in 3xTg-AD mice versus non-transgenic controls. Taken together, our data indicate that neuronal cell cycle reactivation is not a prominent feature induced by Aβ or tau pathology, but rather appears to be triggered by acute neuronal loss.
Katsue Miyoshi, Yasumasa Ohyagi, Nobutaka Sakae, Kyoko Motomura, Linqing Ma, Takayuki Taniwaki, Hirokazu Furuya, Takeshi Tabira, Jun-ichi Kira
Enhancement of Activation of Caspases by Presenilin 1 Gene Mutations and its Inhibition by Secretase Inhibitors
Abstract: Presenilin 1 (PS1) gene mutations are the major causes of early-onset familial Alzheimer's disease. Acceleration of apoptosis is one of the major pathogeneses of PS1 mutants, and PS1 mutants have also been reported to induce overproduction of amyloid-β protein 42. Here, we investigated aberrancy in activation of initiator caspases related to two PS1 gene mutations, I143T and G384A. Acceleration of apoptosis, elevation of caspase-3/7 activity, and significant increases in caspase-4, -8 and -9 activities during apoptosis induced by several agents were found in these mutant PS1-transfected cells. Interestingly, thapsigargin treatment enhanced caspase-4 and -9 activities in I143T-mutant PS1-transfected cells, while hydrogen peroxide treatment enhanced caspase-4, -8 and -9 activities in G384A-mutant PS1-transfected cells, indicating diverse apoptosis-promoting effects of PS1 gene mutations. In addition, treatment with a β-secretase inhibitor or γ-secretase inhibitor significantly attenuated the effects of the PS1 mutants on caspase-3/7 activation and recovered cell viability. Our present data suggest that these PS1 mutants accelerate the activation of initiator caspases and promote apoptosis, which may be associated, at least in part, with amyloid-β production.
Linqing Ma, Yasumasa Ohyagi, Katsue Miyoshi, Nobutaka Sakae, Kyoko Motomura, Takayuki Taniwaki, Hirokazu Furuya, Kazuya Takeda, Takeshi Tabira, Jun-ichi Kira
Increase in p53 Protein Levels by Presenilin 1 Gene Mutations and its Inhibition by Secretase Inhibitors
Abstract: Presenilin 1 (PS1) gene mutations are the major causes of early-onset familial Alzheimer's disease and are known to increase amyloid-β42 (Aβ42) production as well as to promote apoptosis. We have recently reported that intracellular Aβ42 activates p53 mRNA expression and promotes p53-dependent apoptosis. Here, we examined the p53 mRNA and protein levels in cells transfected with wild-type and I143T/G384A mutant PS1 genes. Although the baseline p53 mRNA levels remained unaltered, the p53 protein levels were significantly elevated in mutant PS1-transfected cells. Treatments with apoptosis-inducing agents induced significant elevation of the p53 protein but not p53 mRNA levels in mutant PS1-transfected cells. Treatment with a β-secretase inhibitor and γ-secretase inhibitor decreased the intracellular Aβ levels in amyloid-β protein precursor (AβPP) and PS1-double transfected cells, and restrained upregulation of the p53 protein levels in the mutant PS1-transfected cells. Also, we found that proteasome activity was decreased in mutant PS1-transfected cells compared to wild-type PS1-transfected cells. Proteasome activity was further decreased in AβPP/PS1-double transfected cells. Taken together, p53-dependent apoptosis upregulated by the I143T/G384A mutant PS1 gene may be associated, at least in part, with intracellular Aβ and proteasome impairment.
McKee J. McClendon, Santiago Hernandez, Kathleen A. Smyth, Alan J. Lerner (Communicated by Marwan Sabbagh)
Memantine and Acetylcholinesterase Inhibitor Treatment in Cases of CDR 0.5 or Questionable Impairment
Abstract: The biological meaning of uncertain dementia ratings (CDR 0.5) and its treatment implications are unclear. Our study examines the frequency of anti-dementia medication use in individuals with CDR 0.5 and the cognitive, behavioral, and demographic factors associated with memantine and acetylcholinesterase inhibitor (AChEI) use. Subjects were drawn from the National Alzheimer Coordinating Center database, which collects data from 30 Alzheimer Disease Centers. There were 2,512 subjects with the following diagnoses: Normal, 11.8%; Mild cognitive impairment, 44.6%; Alzheimer’s disease, 34.9%; and other dementias, 8.7%. Overall, 35% used AChEIs and 13% used memantine. AChEI and memantine use was greater in subjects who were referred by clinics and diagnosed with Alzheimer’s disease. AChEI use was associated with being married, younger, male, and more educated while memantine use was associated with less severe apathy and other dementia diagnosis. Non-Hispanic whites were more likely to use AChEI and memantine than non-Hispanic blacks (OR=2.2,2.5). Hispanics were more likely to use AChEI than non-Hispanic blacks. It appears anti-dementia medication use in CDR 0.5 is frequent and represents evidence for extensive off label usage. Diagnosis, severity of impairment, and race, among other variables, affect the likelihood of AChEI and memantine use in this population.
Ming Tong, Matthew Dong, Suzanne M. de la Monte
Brain Insulin-Like Growth Factor and Neurotrophin Resistance in Parkinson’s Disease and Dementia with Lewy Bodies: Potential Role of Manganese Neurotoxicity
Abstract: Parkinson’s disease (PD) and dementia with Lewy bodies (DLB) frequently overlap with Alzheimer’s disease, which is linked to brain impairments in insulin, insulin-like growth factor (IGF), and neurotrophin signaling. We explored whether similar abnormalities occur in PD or DLB, and examined the role of manganese toxicity in PD/DLB pathogenesis. Quantitative RT-PCR demonstrated reduced expression of insulin, IGF-II, and insulin, IGF-I, and IGF-II receptors (R) in PD and/or DLB frontal white matter and amygdala, and reduced IGF-IR and IGF-IIR mRNA in DLB frontal cortex. IGF-I and IGF-II resistance was present in DLB but not PD frontal cortex, and associated with reduced expression of Hu, nerve growth factor, and Trk neurotrophin receptors, and increased levels of glial fibrillary acidic protein, α-synuclein, dopamine-β-hydroxylase, 4-hydroxy-2-nonenal (HNE), and ubiquitin immunoreactivity. MnCl2 treatment reduced survival, ATP, and insulin, IGF-I and IGF-II receptor expression, and increased α-synuclein, HNE, and ubiquitin immunoreactivity in cultured neurons. The results suggest that: 1) IGF-I, IGF-II, and neurotrophin signaling are more impaired in DLB than PD, corresponding with DLB’s more pronounced neurodegeneration, oxidative stress, and α-synuclein accumulation; 2) MnCl2 exposure causes PD/DLB associated abnormalities in central nervous system neurons, and therefore may contribute to their molecular pathogenesis; and 3) molecular abnormalities in PD/DLB overlap with but are distinguishable from Alzheimer’s disease.
Maartje I. Kester, Marinus A. Blankenstein, Femke H. Bouwman, Evert J. van Elk, Philip Scheltens, Wiesje M. van der Flier (Communicated by Sanna-Kaisa Herukka)
CSF Biomarkers in Alzheimer’s Disease and Controls: Associations with APOE Genotype are Modified by Age
Abstract: The object of this study was to elucidate the effect of age in the relationship between APOE genotype and CSF biomarkers amyloid-β1-42 (Aβ42), total tau (tau) and tau phosphorylated at threonine 181 (ptau-181) in AD and controls. 302 AD patients and 174 controls were categorized into APOE ε4 carriers and non-carriers, and into younger and older (≥65years). In controls, older age and APOE ε4 were independently associated with lower Aβ42 and higher tau and ptau-181 levels (p<0.05). For tau and ptau-181, there were also interactions (p<0.10): older carriers had higher levels than older non-carriers, without effect for younger controls. In AD, APOE ε4 genotype had a main effect on Aβ42, but there was also an interaction: older carriers had lower Aβ42 than older non-carriers, without effect for younger AD patients (p<0.05). For tau and ptau-181, there were only interactions: older carriers had higher levels than older non-carriers, while younger AD patients showed the opposite (p≤0.05). Association between CSF biomarkers and APOE genotype were modified by age in both controls and AD patients. This suggests that cognitively healthy APOE ε4 carriers are more prone to develop AD pathology with aging. For AD patients, this provides support for the existence of subtypes within the disease.
Emma R.L.C. Vardy, Penny J. Rice, Peter C.W. Bowie, John D. Holmes, Andrew J. Catto, Nigel M. Hooper (Communicated by Ruth Itzhaki)
Plasma Angiotensin-Converting Enzyme in Alzheimer’s Disease
Abstract: The insertion allele in the gene encoding angiotensin-converting enzyme (ACE) is a risk factor for Alzheimer’s disease (AD) and ACE is one of several peptidases that have the ability to degrade the neurotoxic amyloid-β peptide. ACE is a membrane-bound peptidase that is also present in a soluble form in plasma as a result of a zinc metalloprotease-mediated shedding event. Here we aimed to determine whether there is a difference in ACE in the plasma of late-onset clinically diagnosed AD patients (n=94) as compared to age-matched non-demented control subjects (n=188). Plasma ACE was lower in the AD subjects as compared to the controls both at baseline (p=0.072) and after two years (p=0.05). There was a greater reduction in plasma ACE in the AD subjects as compared to the control subjects over the two years. Plasma ACE did not correlate with cognitive function. The observed reduction in plasma ACE in AD may reflect a general decrease in the zinc metalloprotease-mediated shedding of a subset of membrane-bound proteins.
Xiaoqin Run, Zhihou Liang, Lan Zhang, Khalid Iqbal, Inge Grundke-Iqbal, Cheng-Xin Gong (Communicated by Xiongwei Zhu)
Anesthesia Induces Phosphorylation of Tau
Abstract: Abnormal hyperphosphorylation and aggregation of microtubule-associated protein tau play a crucial role in neurodegeneration of Alzheimer’s disease (AD). Anesthesia has been associated with cognitive impairment and the risk for AD. Here we investigated the effects of anesthesia on site-specific tau phosphorylation and the possible mechanisms. We found that anesthesia for short periods (30 sec to 5 min) induced tau phosphorylation at Thr181, Ser199, Thr205, Thr212, Ser262, and Ser404 to small, but significant, extents, which appeared to result from anesthesia-induced activation of stress-activated protein kinases. Anesthesia for a longer time (1 h) induced much more dramatic phosphorylation of tau at the above sites, and the further phosphorylation may be associated with hypothermia induced by anesthesia. Anesthesia-induced tau phosphorylation appears to be specific because the increased phosphorylation was only seen at half of the tau phosphorylation sites studied and was not observed in global brain proteins. These studies clarified the dynamic changes of tau phosphorylation at various sites and, thus, served as a fundamental guide for future studies on tau phosphorylation by using brains of anesthetized experimental animals. Our findings also provide a possible mechanism by which anesthesia may cause postoperative cognitive impairment and increase the risk for AD.
Edna Grünblatt, Jasmin Bartl, Sonja Zehetmayer, Thomas M. Ringel, Peter Bauer, Peter Riederer, Christian P. Jacob
Gene Expression as Peripheral Biomarkers for Sporadic Alzheimer’s Disease
Abstract: Alzheimer’s disease (AD), the most common cause of dementia, is a progressive neurodegenerative disease. To date, diagnosis availability of AD is rather in the late phase of the disease. Therefore, we attempt to find peripheral biomarkers for early diagnosis of AD. In a pilot recruitment, we investigated the profiles of 33 genes, previously found by our group to alter their expression in postmortem brains of AD. The gene profiles were studied via quantitative-real-time-reverse-transcription-polymerase-chain-reaction, in whole blood samples (collected with the PAXgeneÔ blood RNA system) isolated from a population clinically diagnosed with AD and healthy controls (1-year period/ up to 4 samples). Five genes showed significant correlation to the dementia score, Mini-Mental State Examination (MMSE). Focusing on the two genes with the smallest p-value, H3-histone and cannabinoid-receptor-2, notably increases in these genes were found in peripheral blood mRNA in subjects with lower MMSE scores. Seasonal variations in gene expression were not significant due to sample size, but seem to vary due to time of sample withdrawal. In conclusion, gene expression profiling might be a promising method to investigating a large population with the aim of an early diagnosis of AD.
Supplementary Data for Grünblatt et al. article.
Rolf Jackisch, Stefan Förster, Miriam Kammerer, Anna K. Rothmaier, Andreas Ehret, Josef Zentner, Thomas J. Feuerstein (Communicated by Marcella Reale)
Inhibitory Potency of Choline Esterase Inhibitors on Acetylcholine Release and Choline Esterase Activity in Fresh Specimens of Human and Rat Neocortex
Abstract: Fresh specimens of human and rat neocortex were used to determine direct and indirect inhibitory potencies of choline esterase inhibitors (ChEIs) on ChE and the release of acetylcholine (ACh), respectively. Km values of ChE in homogenates of rat and human neocortex did not differ significantly, whereas the specific activity of ChE was >2 times higher in the rat. Butyryl ChE exhibited a higher Km and a lower specific activity than ACh esterase in human neocortex. Inhibition of ChE in rat and human tissue was similar [IC50 (nM; human): donepezil: 14, physostigmine: 22, tacrine: 95, galanthamine: 575, rivastigmine: 9120]. In neocortex slices preincubated with [3H]choline the electrically evoked release of [3H]ACh was inhibited up to 60% by ChEIs (IC50 (nM, rat): donepezil: 30, physostigmine: 39, tacrine: 302, galanthamine: 646, rivastigmine: >10000). Similar IC50-values were also estimated for ACh release in human neocortex, although the maximal inhibitory effects were much smaller (~20%). We conclude that in comparison to rats: 1) neocortical ChE concentrations are lower and 2) that ChEIs have weaker indirect (muscarine receptor-mediated) presynaptic inhibitory effects in the human brain. We further suggest that a combination of ChEIs with brain-selective muscarine autoreceptor antagonists might help to improve their clinical efficacy.
Thomas Leyhe, Gerhard W. Eschweiler, Elke Stransky, Thomas Gasser, Peter Annas, Hans Basun, Christoph Laske (Communicated by Jesus Avila)
Increase of BDNF Serum Concentration in Lithium Treated Patients with Early Alzheimer’s Disease
Abstract: Preclinical and clinical studies gave evidence that lithium could be useful in the treatment of Alzheimer’s disease (AD). In experimental investigations, lithium induces brain-derived neurotrophic factor (BDNF). Recent studies have found a decrease of BDNF in the serum and brains of AD patients with potentially consecutive lack of neurotrophic support. We assessed the influence of a lithium treatment on BDNF serum concentration in a subset of a greater sample recruited for a randomized, single-blinded, placebo-controlled, parallel-group multicenter 10-week study, investigating the efficacy of lithium treatment in AD patients. In AD patients treated with lithium, a significant increase of BDNF serum levels, and additionally a significant decrease of ADAS-Cog sum scores in comparison to placebo-treated patients, was found. Diminution of cognitive impairment was inversely correlated with lithium serum concentration. Upregulation of BDNF might be part of a neuroprotective effect of lithium in AD patients. The results of the present investigation encourage performing studies with longer treatment phases to observe potential positive long-term effects of lithium in AD patients.
Transcript of Live Discussion held at the Alzheimer Research Forum
Alzheimer Research Forum Live Discussion: Sports Concussions, Dementia, and APOE Genotyping: What Can Scientists Tell the Public? What’s Up for Research?